Member for nonaqueous electrolyte batteries

ABSTRACT

A member for a non-aqueous electrolyte battery containing a copolymer containing a tetrafluoroethylene unit and a fluoroalkyl vinyl ether unit, in which the number of functional groups per 10 6  carbon atoms of a main chain of the copolymer is 100 or less, and a melt flow rate of the copolymer is less than 20 g/10 minutes.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Rule 53(b) Continuation of InternationalApplication No. PCT/JP2020/032236 filed Aug. 26, 2020, which claimspriority based on Japanese Patent Application No. 2019-153773 filed Aug.26, 2019 and Japanese Patent Application No. 2020-038592 filed Mar. 6,2020, the respective disclosures of which are incorporated herein byreference in their entireties.

TECHNICAL FIELD

The present disclosure relates to a member for a non-aqueous electrolytebattery.

BACKGROUND ART

Tetrafluoroethylene/fluoroalkyl vinyl ether copolymers have favorableinsulating characteristics and are thus used for insulating members orthe like for batteries.

For example, Patent Document 1 discloses a battery including an exteriorcan, an electrode group that is accommodated in the exterior can andincludes a positive electrode and a negative electrode, a lid that ismounted in an opening portion of the exterior can, a terminal portion ofthe positive electrode and a terminal portion of the negative electrode,in which at least one of the terminal portion of the positive electrodeand the terminal portion of the negative electrode includes a throughhole opened in the lid and an insulating gasket having a tubular portionthat is intercalated into the through hole of the lid, and the resinthat forms the insulating gasket is a tetrafluoroethylene-perfluoroalkylvinyl ether copolymer.

CITATION LIST Patent Literature

-   Patent Literature 1: Japanese Patent Laid-Open No. 2011-48976

SUMMARY

According to the present disclosure, there is provided a member for anon-aqueous electrolyte battery containing a copolymer containing atetrafluoroethylene unit and a fluoroalkyl vinyl ether unit, in whichthe number of functional groups per 10⁶ carbon atoms of a main chain ofthe copolymer is 100 or less, and a melt flow rate of the copolymer isless than 20 g/10 minutes.

Effects

According to the present disclosure, it is possible to provide a memberfor a non-aqueous electrolyte battery having excellent resistance tocompression set at high temperatures.

BRIEF DESCRIPTION OF DRAWINGS

The FIGURE is a graph showing the concentrations (ppm) of fluorine ionseluted, as measured in the immersion tests of test pieces produced inExamples 1 to 3 and Comparative Example 1 in an electrolytic solution.

DESCRIPTION OF EMBODIMENTS

Hereinafter, specific embodiments of the present disclosure will bedescribed in detail, but the present disclosure is not limited to thefollowing embodiments.

A member for a non-aqueous electrolyte battery of the present disclosurecontains a copolymer containing a tetrafluoroethylene unit and afluoroalkyl vinyl ether (FAVE) unit.

The copolymer contained in the member for a non-aqueous electrolytebattery of the present disclosure is a melt-fabricable fluororesin.Being melt-fabricable means that polymers can be melted and fabricatedusing a conventional fabricating device such as an extruder or aninjection molding device.

FAVE for giving the FAVE unit can be at least one selected from thegroup consisting of monomers represented by the general formula (1):

CF₂═CFO(CF₂CFY¹O)_(p)—(CF₂CF₂CF₂O)_(q)—Rf  (1)

wherein, Y¹ represents F or CF₃, Rf represents a perfluoroalkyl grouphaving 1 to 5 carbon atoms, p represents an integer of 0 to 5, and qrepresents an integer of 0 to 5; and monomers represented by the generalformula (2):

CFX═CXOCF₂OR¹  (2)

wherein, Xs are the same or different from each other and each representH, F or CF₃, and R¹ represents a linear or branched fluoroalkyl grouphaving 1 to 6 carbon atoms and optionally having one or two atoms of atleast one selected from the group consisting of H, Cl, Br and I or acyclic fluoroalkyl group having 5 or 6 carbon atoms and optionallyhaving one or two atoms of at least one selected from the groupconsisting of H, Cl, Br and I.

Among them, the FAVE is preferably the monomers represented by thegeneral formula (1), more preferably at least one selected from thegroup consisting of perfluoro(methyl vinyl ether), perfluoro(ethyl vinylether) (PEVE) and perfluoro(propyl vinyl ether) (PPVE), still morepreferably at least one selected from the group consisting of PEVE andPPVE and particularly preferably PPVE.

The content of the fluoroalkyl vinyl ether (FAVE) unit in the copolymeris preferably 1.0 to 10.0 mass %, more preferably 2.0 mass % or more,still more preferably 3.0 mass % or more, far still more preferably 3.5mass % or more, particularly preferably 4.0 mass % or more and mostpreferably 5.6 mass % or more, and more preferably 8.0 mass % or less,still more preferably 7.0 mass % or less, particularly preferably 6.5mass % or less and most preferably 6.0 mass % or less, based on all ofthe monomer units. When the content of the FAVE unit in the copolymer iswithin the above-described range, more excellent resistance tocompression set at high temperatures of the member for a non-aqueouselectrolyte battery can be obtained.

The content of the tetrafluoroethylene (TFE) unit in the copolymer ispreferably 99.0 to 90.0 mass %, more preferably 98.0 mass % or less,still more preferably 97.0 mass % or less, far still more preferably96.5 mass % or less, particularly preferably 96.0 mass % or less andmost preferably 94.4 mass % or less, and more preferably 92.0 mass % ormore, still more preferably 93.0 mass % or more, particularly preferably93.5 mass % or more and most preferably 94.0 mass % or more, based onall of the monomer units. When the content of the TFE unit in thecopolymer is within the above-described range, more excellent resistanceto compression set at high temperatures of the member for a non-aqueouselectrolyte battery can be obtained.

In the present disclosure, the content of each monomer unit in thecopolymer is measured by the ¹⁹F-NMR method.

The copolymer may also contain a monomer unit derived from a monomercopolymerizable with TFE and FAVE. In this case, the content of themonomer copolymerizable with TFE and FAVE is preferably 0 to 10 mass %,more preferably 0.1 to 2.0 mass % and still more preferably 0.1 to 0.4mass %, based on all of the monomer units in the copolymer.

Examples of the monomer copolymerizable with TFE and FAVE include HFP, avinyl monomer represented by CZ¹Z²═CZ³ (CF₂)_(n)Z⁴, wherein, Z¹, Z² andZ³ are the same or different from one another and each represent H or F,Z⁴ represents H, F or Cl, and n represents an integer of 2 to 10, and analkyl perfluorovinyl ether derivative represented by CF₂═CF—OCH₂—Rf¹,wherein, Rf¹ represents a perfluoroalkyl group having 1 to 5 carbonatoms. Among them, HFP is preferable.

The copolymer is preferably at least one selected from the groupconsisting of a copolymer consisting of the TFE unit and the FAVE unitand a TFE/HFP/FAVE copolymer and more preferably a copolymer consistingof the TFE unit and the FAVE unit.

The melting point of the copolymer is preferably 280° C. to 322° C.,more preferably 285° C. or higher and still more preferably 295° C. orhigher, and more preferably 320° C. or lower, still more preferably 315°C. or lower and particularly preferably 310° C. or lower, in view ofheat resistance and stress crack resistance. The melting point can bemeasured using a differential scanning calorimeter (DSC).

The glass transition temperature (Tg) of the copolymer is preferably 70°C. or higher, more preferably 80° C. or higher, still more preferably85° C. or higher, far still more preferably 90° C. or higher,particularly preferably 95° C. or higher and most preferably 100° C. orhigher. The glass transition temperature can be measured by measuringdynamic viscoelasticity.

The melt flow rate of the copolymer is less than 20 g/10 minutes,preferably 19 g/10 minutes or less, more preferably 18 g/10 minutes orless and still more preferably 17 g/10 minutes or less, and due to sucha melt flow rate, the resistance to compression set at high temperaturesof the member for a non-aqueous electrolyte battery further improves.The melt flow rate of the copolymer is preferably 5 g/10 minutes ormore, more preferably 8 g/10 minutes or more, still more preferably 11g/10 minutes or more and particularly preferably 13 g/10 minutes ormore, in view of relatively easily manufacturing the member for anon-aqueous electrolyte battery without significantly impairing themoldability of the copolymer.

In the present disclosure, the melt flow rate is a value that isobtained in terms of the mass of a polymer that flows out from a nozzlehaving an inner diameter of 2.1 mm and a length of 8 mm per 10 minutes(g/10 minutes) at 372° C. under a load of 5 kg using a melt indexeraccording to ASTM D1238.

The number of functional groups per 10⁶ carbon atoms of the main chainof the copolymer contained in the member for a non-aqueous electrolytebattery of the present disclosure is 100 or less. Since the member for anon-aqueous electrolyte battery of the present disclosure contains thecopolymer in which the number of functional groups per 10⁶ carbon atomsof the main chain is 100 or less, the member for a non-aqueouselectrolyte battery has a low compression set rate at high temperaturesand also excellent swelling resistance to non-aqueous electrolyticsolutions, and furthermore, does not easily allow fluorine ions to beeluted into non-aqueous electrolytic solutions.

The number of functional groups per 10⁶ carbon atoms of the main chainof the copolymer is preferably 80 or less, more preferably 50 or lessand still more preferably 20 or less, in view of obtaining moreexcellent resistance to compression set at high temperatures of themember for a non-aqueous electrolyte battery.

Infrared spectroscopy can be used for identifying the functional groupsand measuring the number of the functional groups.

Specifically, the number of the functional groups is measured by thefollowing method. First, the copolymer is molded by cold press toproduce a film having a thickness of 0.25 to 0.3 mm. This film isanalyzed by the Fourier transform infrared spectroscopy to obtain theinfrared absorption spectrum of the copolymer, and a differentialspectrum between the resulting infrared absorption spectrum and a basespectrum of a completely-fluorinated copolymer with no functional groupsis obtained. The number of functional groups per 1×10⁶ carbon atoms inthe copolymer, N, is calculated from the absorption peak of a specificfunctional group appearing in this differential spectrum according tothe following formula (A).

N=I×K/t  (A)

I: Absorbance

K: Coefficient of correction

t: Thickness of film (mm)

For reference, the absorption frequencies, coefficients of molarabsorbance and coefficients of correction of the functional groups inthe present disclosure are shown in Table 1. The coefficients of molarabsorbance have been determined from the FT-IR measurement data oflow-molecular model compounds.

TABLE 1 Absorption Molar Frequency Extinction Correction FunctionalGroup (cm⁻¹) Coefficient Factor Model Compound —COF 1883 600 388C₇F₁₅COF —COOH free 1815 530 439 H(CF₂)₆COOH —COOH bonded 1779 530 439H(CF₂)₆COOH —COOCH₃ 1795 680 342 C₇F₁₅COOCH₃ —CONH₂ 3436 506 460C₇H₁₅CONH₂ —CH₂OH₂, —OH 3648 104 2236 C₇H₁₅CH₂OH —CF₂H 3020 8.8 26485H(CF₂CF₂)₃CH₂OH —CF═CF₂ 1795 635 366 CF₂═CF₂

The absorption frequencies of —CH₂CF₂H, —CH₂COF, —CH₂COOH, —CH₂COOCH₃and —CH₂CONH₂ are lower by several tens of kayser (cm⁻¹) from theabsorption frequencies of —CF₂H, —COF, —COOH free and —COOH bonded,—COOCH₃ and —CONH₂, which are shown in the table, respectively.

Therefore, for example, the number of functional groups —COF is thetotal of the number of functional groups obtained from an absorptionpeak at an absorption frequency of 1,883 cm⁻¹ assigned to —CF₂COF andthe number of functional groups obtained from an absorption peak at anabsorption frequency of 1,840 cm⁻¹ assigned to —CH₂COF.

The functional groups are a functional group that is present at a mainchain terminal or at a side chain terminal in the copolymer and afunctional group that is present in the main chain or in a side chain inthe copolymer. The number of functional groups may be the total numberof —CF═CF₂, —CF₂H, —COF, —COOH, —COOCH₃, —CONH₂ and —CH₂OH.

The functional groups are introduced into the copolymer with, forexample, a chain transfer agent or a polymerization initiator that isused at the time of producing the copolymer. For example, in a casewhere an alcohol is used as a chain transfer agent or a peroxide havinga structure of —CH₂OH is used as a polymerization initiator, —CH₂OH isintroduced into a main chain terminal in the copolymer. In addition, thefunctional groups are introduced into side chain terminals in thecopolymer by the polymerization of monomers having a functional group.

When such a copolymer having a functional group is subjected tofluorination treatment, it is possible to obtain the copolymer in whichthe number of functional groups is within the above-described range. Inother words, the copolymer contained in the member for a non-aqueouselectrolyte battery of the present disclosure is preferably a copolymerthat has been subjected to fluorination treatment. The copolymercontained in the member for a non-aqueous electrolyte battery of thepresent disclosure also preferably has a —CF₃ terminal group.

The fluorination treatment can be carried out by contacting a copolymerthat has not been subjected to fluorination treatment with afluorine-containing compound.

The fluorine-containing compound is not limited and can be a fluorineradical source that generates a fluorine radical under a fluorinationtreatment condition. Examples of the fluorine radical source include F₂gas, CoF₃, AgF₂, UF₆, OF₂, N₂F₂, CF₃OF, and a halogen fluoride (forexample, IF₅ or ClF₃).

The fluorine radical source such as F₂ gas may have a concentration of100%, but is preferably used after being diluted to 5 to 50 mass % andmore preferably used after being diluted to 15 to 30 mass % by mixingthe fluorine radical source with an inert gas, in view of safety.Examples of the inert gas include nitrogen gas, helium gas, and argongas, and the inert gas is preferably nitrogen gas from an economicalviewpoint.

The conditions for the fluorination treatment are not limited. Thecopolymer in a molten state may be contacted with thefluorine-containing compound, and normally the copolymer can becontacted with the fluorine-containing compound at a temperature of themelting point or lower of the copolymer, preferably 20° C. to 240° C.,more preferably 80° C. to 240° C. and still more preferably 100° C. to220° C. The fluorination treatment is carried out for, ordinarily, 1 to30 hours and preferably 5 to 25 hours. In the fluorination treatment, acopolymer that has not been subjected to fluorination treatment ispreferably contacted with fluorine gas (F₂ gas).

The copolymer used in the fluorination treatment can be produced by, forexample, a known conventional method including appropriately mixingmonomers that serve as constituent units of the copolymer and anadditive such as a polymerization initiator and carrying out emulsionpolymerization or suspension polymerization.

The member for a non-aqueous electrolyte battery of the presentdisclosure may also contain other components as necessary. Examples ofthe other components include a filler, a plasticizer, a pigment, acolorant, an antioxidant, a UV absorber, a flame retarder, an anti-agingagent, an antistatic agent, and an antibacterial agent.

Among them, the other component is preferably a filler. Examples of thefiller include silica, kaolin, clay, organic clay, talc, mica, alumina,calcium carbonate, calcium terephthalate, titanium oxide, calciumphosphate, calcium fluoride, lithium fluoride, crosslinked polystyrene,potassium titanate, carbon, boron nitride, a carbon nanotube, and aglass fiber.

As described above, the member for a non-aqueous electrolyte battery ofthe present disclosure may contain the other components in addition tothe copolymer. However, in view of further exhibiting the excellentcharacteristics of the copolymer sufficiently, the content of the othercomponents is preferably as small as possible, and the other componentsare most preferably not contained. Specifically, the content of othercomponents are preferably 30 mass % or less, more preferably 10 mass %or less and most preferably 0 mass %, based on the member for anon-aqueous electrolyte battery of the present disclosure. That is, themember for a non-aqueous electrolyte battery of the present disclosuremost preferably does not contain any other components. The member for anon-aqueous electrolyte battery of the present disclosure may consist ofthe copolymer.

The member for a non-aqueous electrolyte battery of the presentdisclosure can be manufactured by molding the copolymer or a compositioncontaining the copolymer and the other components into a desired shapeor size. A method for producing the composition can be a method in whichthe copolymer and the other components are mixed in a dry manner, and amethod in which the copolymer and the other components are mixed inadvance with a mixer and then melted and kneaded with a kneader, a meltextruder or the like.

A method for molding the copolymer or the composition is not limited andexamples thereof include an injection molding method, an extrusionmethod, a compression molding method, and a blow molding method. Amongthem, the compression molding method or the injection molding method ispreferable and the injection molding method is more preferable since themember for a non-aqueous electrolyte battery can be produced with highproductivity. That is, the member for a non-aqueous electrolyte batteryof the present disclosure is preferably a compression molded article oran injection molded article and more preferably an injection moldedarticle since the member for a non-aqueous electrolyte battery can beproduced with high productivity.

The member for a non-aqueous electrolyte battery of the presentdisclosure exhibits a low compression set rate even when deformed at ahigh compressive deformation rate. The member for a non-aqueouselectrolyte battery of the present disclosure can be used in acompressively deformed state at a compressive deformation rate of 10% ormore and can be used in a compressively deformed state at a compressivedeformation rate of 20% or more or 25% or more. When the member for anon-aqueous electrolyte battery of the present disclosure is used in adeformed state at such a high compressive deformation rate, the memberis capable of maintaining certain rebound resilience for a long periodof time and therefore maintaining sealing characteristics and insulatingcharacteristics for a long period of time.

In addition, the member for a non-aqueous electrolyte battery of thepresent disclosure exhibits a low compression set rate even whendeformed at a high compressive deformation rate at a high temperature.The member for a non-aqueous electrolyte battery of the presentdisclosure can be used in a compressively deformed state at acompressive deformation rate of 10% or more at 150° C. or higher and canbe used in a compressively deformed state at a compressive deformationrate of 20% or more or 25% or more at 150° C. or higher. When the memberfor a non-aqueous electrolyte battery of the present disclosure is usedin a deformed state at a high compressive deformation rate at such ahigh temperature, the member is capable of maintaining certain reboundresilience for a long period of time and therefore capable ofmaintaining sealing characteristics and insulating characteristics athigh temperatures for a long period of time.

The compressive deformation rate refers to a compressive deformationrate at a portion where the compressive deformation rate is highest whenthe member for a non-aqueous electrolyte battery is used in a compressedstate. For example, in a case where a flat member for a non-aqueouselectrolyte battery is used in a state where the member is compressed inthe thickness direction, the compressive deformation rate refers to thecompressive deformation rate in the thickness direction. For example, ina case where the member for a non-aqueous electrolyte battery is used ina state where only a part of the member for a non-aqueous electrolytebattery is compressed, the compressive deformation rate refers to thecompressive deformation rate at a portion where the compressivedeformation rate is highest, among the compressive deformation rates atcompressed portions.

The size or shape of the member for a non-aqueous electrolyte battery ofthe present disclosure may be appropriate to the use, and is notlimited. The shape of the member for a non-aqueous electrolyte batteryof the present disclosure may be, for example, cyclic. The member for anon-aqueous electrolyte battery of the present disclosure may have acircular shape, an oval shape, a quadrilateral shape with roundedcorners, or the like in planar view, with a through hole in the centralportion.

The member for a non-aqueous electrolyte battery of the presentdisclosure is a member for constituting non-aqueous electrolyticsolution batteries. The member for a non-aqueous electrolyte battery ofthe present disclosure is excellent in swelling resistance tonon-aqueous electrolytic solutions and, furthermore, does not easilyallow fluorine ions to be eluted into non-aqueous electrolyticsolutions, and accordingly, the member is particularly preferable as amember that is used in a state where the member is in contact withnon-aqueous electrolytic solutions in non-aqueous electrolytic solutionbatteries. That is, the member for a non-aqueous electrolyte battery ofthe present disclosure may have a liquid-contact surface withnon-aqueous electrolytic solutions in non-aqueous electrolytic solutionbatteries.

The member for a non-aqueous electrolyte battery of the presentdisclosure contains the copolymer having a reduced number of functionalgroups and thus also exhibits the surprising effect of not easilyallowing fluorine ions to be eluted into non-aqueous electrolyticsolutions. Therefore, the use of the member for a non-aqueouselectrolyte battery of the present disclosure makes it possible tosuppress an increase in the concentration of fluorine ions innon-aqueous electrolytic solutions. As a result, the use of the memberfor a non-aqueous electrolyte battery of the present disclosure makes itpossible to suppress the generation of gas such as HF in non-aqueouselectrolytic solution batteries or makes it possible to suppressdeterioration of the battery performance and shortening of the servicelives of non-aqueous electrolytic solution batteries.

In addition, taking into consideration that the member for a non-aqueouselectrolyte battery of the present disclosure is capable of furthersuppressing the generation of gas such as HF in non-aqueous electrolyticsolution batteries or capable of further suppressing deterioration ofthe battery performance and suppressing shortening of the service livesof non-aqueous electrolytic solution batteries, the amount of fluorineions eluted and detected in an immersion test in an electrolyticsolution is preferably 1 ppm or less, preferably 0.8 ppm or less andmore preferably 0.7 ppm or less in terms of mass. The immersion test inan electrolytic solution can be carried out by producing a test piecehaving a weight equivalent to 10 molded articles (15 mm×15 mm×0.2 mm)from the member for a non-aqueous electrolyte battery, putting a glasssample bottle including the test piece and 2 g of dimethyl carbonate(EMC) into a constant-temperature vessel at 80° C., and leaving thesample bottle to stand for 24 to 144 hours (preferably 144 hours).

The non-aqueous electrolyte battery is not limited as long as thebattery contains a non-aqueous electrolytic solution, and examplesthereof include a lithium ion secondary battery and a lithium ioncapacitor. Members that constitute the non-aqueous electrolyte batteryinclude a sealing member and an insulating member.

The non-aqueous electrolytic solution is not limited and one or more ofknown solvents such as propylene carbonate, ethylene carbonate, butylenecarbonate, γ-butyl lactone, 1,2-dimethoxyethane, 1,2-diethoxyethane,dimethyl carbonate, diethyl carbonate and ethyl methyl carbonate can beused. The non-aqueous electrolyte battery may further contain anelectrolyte. The electrolyte is not limited and LiClO₄, LiAsF₆, LiPF₆,LiBF₄, LiCl, LiBr, CH₃SO₃Li, CF₃SO₃Li, cesium carbonate or the like canbe used.

The member for a non-aqueous electrolyte battery of the presentdisclosure can be preferably used as, for example, a sealing member suchas a sealing gasket or a sealing packing, or an insulating member suchas an insulating gasket or an insulating packing. The sealing memberrefers to a member that is used to prevent the leakage of liquid or gasor the intrusion of liquid or gas from the outside. The insulatingmember refers to a member that is used to insulate electricity. Themember for a non-aqueous electrolyte battery of the present disclosuremay be a member that is used for the purpose of both sealing andinsulation.

The member for a non-aqueous electrolyte battery of the presentdisclosure exhibits a low compression set rate even after compressed ata high temperature and thus can be preferably used in environments wheretemperatures become high. For example, the member for a non-aqueouselectrolyte battery of the present disclosure is preferably used inenvironments where the highest temperature reaches 40° C. or higher.Furthermore, the member for a non-aqueous electrolyte battery of thepresent disclosure is preferably used in environments where the highesttemperature reaches, for example, 150° C. or higher. Examples of a casewhere the member for a non-aqueous electrolyte battery of the presentdisclosure may reach such a high temperature include a case where amember for a non-aqueous electrolyte battery is mounted in a compressedstate in a battery, followed by mounting another battery member in thebattery by welding, and a case where a non-aqueous electrolyte batterygenerates heat.

The member for a non-aqueous electrolyte battery of the presentdisclosure exhibits a low compression set rate even after compressed ata high temperature, is excellent in swelling resistance to non-aqueouselectrolytic solutions, and furthermore, does not easily allow fluorineions to be eluted into non-aqueous electrolytic solutions, and thus themember can be preferably used as a sealing member for non-aqueouselectrolytic solution batteries or an insulating member for non-aqueouselectrolytic solution batteries. For example, at the time of charging abattery such as a non-aqueous electrolytic solution secondary battery,there is a case where the temperature of the battery temporarily reaches40° C. or higher, and particularly, temporarily reaches 150° C. orhigher. The member for a non-aqueous electrolyte battery of the presentdisclosure has high rebound resilience that is not impaired even whenthe member for a non-aqueous electrolyte battery is used in a deformedstate at a high compressive deformation rate at a high temperature and,furthermore, in a state where the member is contacted with non-aqueouselectrolytic solutions at a high temperature, in batteries such as anon-aqueous electrolytic solution secondary battery. Therefore, in acase where the member for a non-aqueous electrolyte battery of thepresent disclosure is used as a sealing member, excellent sealingcharacteristics are maintained for a long period of time. In addition,the member for a non-aqueous electrolyte battery of the presentdisclosure contains the copolymer described above and thus has excellentinsulating characteristics. Therefore, in a case where the member for anon-aqueous electrolyte battery of the present disclosure is used as aninsulating member, the member for a non-aqueous electrolyte batteryfirmly adheres to two or more electrically conductive members to preventshort-circuiting for a long period of time.

Hereinabove, the embodiments have been described, but it is understoodthat the embodiments or the details can be modified in a variety ofmanners without departing from the gist and scope of the claims.

According to the present disclosure, there is provided a member for anon-aqueous electrolyte battery containing a copolymer containing atetrafluoroethylene unit and a fluoroalkyl vinyl ether unit, in whichthe number of functional groups per 10⁶ carbon atoms of a main chain ofthe copolymer is 100 or less, and a melt flow rate of the copolymer isless than 20 g/10 minutes.

In the member for a non-aqueous electrolyte battery of the presentdisclosure, the copolymer preferably has a melting point of 295° C. to320° C.

In the member for a non-aqueous electrolyte battery of the presentdisclosure, a content of the fluoroalkyl vinyl ether unit in thecopolymer is preferably 1.0 to 10.0 mass % based on all monomer units.

In the member for a non-aqueous electrolyte battery of the presentdisclosure, the fluoroalkyl vinyl ether unit is preferably aperfluoro(propyl vinyl ether) unit.

The member for a non-aqueous electrolyte battery of the presentdisclosure can be used in a compressively deformed state at acompressive deformation rate of 10% or more.

The member for a non-aqueous electrolyte battery of the presentdisclosure preferably has a liquid-contact surface with a non-aqueouselectrolytic solution.

In the member for a non-aqueous electrolyte battery of the presentdisclosure, an amount of fluorine ions eluted and detected in animmersion test in an electrolytic solution is preferably 1 ppm or less.

The member for a non-aqueous electrolyte battery of the presentdisclosure is preferably an injection molded article.

The member for a non-aqueous electrolyte battery of the presentdisclosure can be preferably used as a sealing member or an insulatingmember.

EXAMPLES

Next, the embodiments of the present disclosure will be described by wayof examples, but the present disclosure is not limited to theseexamples.

Individual numerical values in the examples were measured by thefollowing methods.

(Content of Monomer Unit)

The content of each monomer unit was measured with an NMR analyzer (forexample, AVANCE 300 high-temperature probe manufactured by BrukerBioSpin K.K.).

(Melt Flow Rate (MFR))

The mass of a polymer that flowed out from a nozzle having an innerdiameter of 2.1 mm and a length of 8 mm per 10 minutes (g/10 minutes) at372° C. under a load of 5 kg was determined using a melt indexer G-01(manufactured by Toyo Seiki Seisaku-sho, Ltd.) according to ASTM D1238.

(Melting Point)

The melting point was determined as a temperature corresponding to themaximum value in a heat-of-fusion curve when heating a polymer at a rateof 10° C./minute using a differential scanning calorimeter (trade name:X-DSC7000 manufactured by Hitachi High-Tech Science Corporation).

(Number of Functional Groups)

Pellets were molded by cold press to produce a film having a thicknessof 0.25 to 0.3 mm. This film was scanned 40 times and analyzed with aFourier transform infrared spectrometer [FT-IR (Spectrum One,manufactured by PerkinElmer Co., Ltd.)] to obtain an infrared absorptionspectrum, and a differential spectrum between the resulting infraredabsorption spectrum and a base spectrum of a completely-fluorinatedcopolymer with no functional groups was obtained. The number offunctional groups per 1×10⁶ carbon atoms, N, in the sample wascalculated from the absorption peak of a specific functional groupappearing in this differential spectrum using the following formula (A).

N=I×K/t  (A)

I: Absorbance

K: Coefficient of correction

t: Thickness of film (mm)

For reference, the absorption frequencies, coefficients of molarabsorbance and coefficients of correction of the functional groups inthe present disclosure are shown in Table 2. The coefficients of molarabsorbance have been determined from the FT-IR measurement data oflow-molecular model compounds.

In the present disclosure, the total of the numbers of —COOH, —COOCH₃,—CH₂OH, —COF, —CF═CF₂, —CONH₂ and —CF₂H is regarded as the number offunctional groups.

TABLE 2 Absorption Molar Frequency Extinction Correction FunctionalGroup (cm⁻¹) Coefficient Factor Model Compound —COF 1883 600 388C₇F₁₅COF —COOH free 1815 530 439 H(CF₂)₆COOH —COOH bonded 1779 530 439H(CF₂)₆COOH —COOCH₃ 1795 680 342 C₇F₁₅COOCH₃ —CONH₂ 3436 506 460C₇H₁₅CONH₂ —CH₂OH₂, —OH 3648 104 2236 C₇H₁₅CH₂OH —CF₂H 3020 8.8 26485H(CF₂CF₂)₃CH₃OH —CF═CF₂ 1795 635 366 CF₂═CF₂

Example 1

The following pellets were obtained in the same manner as in themanufacturing method described in Example 2 of International PublicationNo. WO 2003/048214.

Formulation: TFE/PPVE=94.4/5.6 (mass %)

MFR: 14.7 (g/10 min)

Melting point: 302° C.

Number of functional groups: Four/10⁶ C

Approximately 5 g of the pellets were placed into a mold (innerdiameter: 120 mm, height: 38 mm), melted at 370° C. for 20 minutes byhot plate press and then cooled with water while being pressurized at apressure of 1 MPa (resin pressure), thereby producing molded articleshaving a thickness of approximately 0.2 nm. After that, 15 mm×15 mm testpieces were produced from the obtained molded articles.

(Immersion Test in Electrolytic Solution)

Ten of the obtained test pieces and 2 g of an electrolytic solution(dimethyl carbonate (DMC)) were put into a 20 mL glass sample bottle,and the sample bottle was closed with a lid. The sample bottle was putinto a constant-temperature vessel at 80° C. and left to stand for 144hours, thereby immersing the test pieces in the electrolytic solution.After that, the sample bottle was taken out from theconstant-temperature vessel and left to cool to room temperature, andthen the test pieces were taken out from the sample bottle. Theelectrolytic solution, which was left after the test pieces were takenout, was dried with an air for 24 hours while the electrolytic solutionwas still kept in the sample bottle in a room controlled at 25° C., and2 g of ultrapure water was added thereto. The obtained aqueous solutionwas transferred to a measurement cell of an ion chromatography system,and the concentration of fluorine ions in this aqueous solution wasmeasured with the ion chromatography system (Dionex ICS-2100manufactured by Thermo Fisher Scientific). The results are shown in theFIGURE.

(Compression Set Rate (CS))

The compression set rate was determined using a method described in ASTMD395 or JIS K 6262.

Approximately 2 g of the pellets were placed into a mold (innerdiameter: 13 mm, height: 38 mm), melted at 370° C. for 30 minutes by hotplate press and then cooled with water while being pressurized at apressure of 0.2 MPa (resin pressure), thereby producing molded articleshaving a height of approximately 8 mm. After that, the obtained moldedarticles were cut, thereby producing test pieces having an outerdiameter of 13 mm and a height of 6 mm. The produced test pieces werecompressed using a compression device at normal temperature at acompressive deformation rate of up to 50% (that is, the test pieceshaving a height of 6 mm were compressed to a height of 3 mm).

Next, the compressed test pieces were placed still in an electricfurnace while being fixed to the compression device, and left to standat 150° C., 170° C. or 190° C. for 18 hours. The compression device wastaken out from the electric furnace and left to cool to roomtemperature, and then the test pieces were removed. The resulting testpieces were left to stand at room temperature for 30 minutes, and thenthe heights were measured. The compression set rates were obtained fromthe following formula. The results are shown in Table 3.

Compression set rate (%)=(t ₀ −t ₂)/(t ₀ −t ₁)×100

-   -   t₀: Original height of test piece (mm)    -   t₁: Height of spacer (mm)    -   t₂: Height of test piece removed from compression device (mm)

In the above-described test, to was 6 mm, and t₁ was 3 mm.

(Temperature for Retaining 2 MPa)

The recovery, t₂−t₁, at each temperature was calculated from the resultsin the measurement of the compression set rate, and a linearapproximation straight line of the relationship between the recovery ofthe TFE/PPVE copolymer and the temperature was produced by plotting thetemperatures and the recoveries. In a case of a compressive deformationrate of 50%, if the elastic modulus of the TFE/PPVE copolymer is assumedto be 600 MPa, the repulsive stress reaches 2 MPa when the recovery is0.01 mm. The temperature where the recovery reached 0.01 mm was obtainedfrom the linear approximation straight line and regarded as atemperature for retaining 2 MPa. The results are shown in Table 3.

Example 2

The following pellets were obtained in the same manner as in amanufacturing method described in Comparative Manufacturing Example 1 ofJapanese Patent Laid-Open No. 2009-059690.

Formulation: TFE/PPVE=93.4/6.6 (mass %)

MFR: 17.1 (g/10 min)

Melting point: 302° C.

Number of functional groups: 20/10⁶ C

Test pieces were produced and an immersion test in an electrolyticsolution was carried out using the obtained test pieces in the samemanner as in Example 1, except that the above-described pellets wereused. The results are shown in the FIGURE. Test pieces were produced andthe compression set rate and the temperature for retaining 2 MPa weredetermined using the obtained test pieces in the same manner as inExample 1, except that the above-described pellets were used. Theresults are shown in Table 3.

Example 3

The following pellets were obtained in the same manner as in amanufacturing method described in Example 6 of International PublicationNo. WO 2003/048214.

Formulation: TFE/PPVE=94.5/5.5 (mass %)

MFR: 6.9 (g/10 min)

Melting point: 302° C.

Number of functional groups: Three/10⁶ C

Test pieces were produced and an immersion test in an electrolyticsolution was carried out using the obtained test pieces in the samemanner as in Example 1, except that the above-described pellets wereused. The results are shown in the FIGURE. Test pieces were produced andthe compression set rate and the temperature for retaining 2 MPa weredetermined using the obtained test pieces in the same manner as inExample 1, except that the above-described pellets were used. Theresults are shown in Table 3.

Comparative Example 1

The following pellets were obtained in the same manner as in amanufacturing method described in Synthesis Example 2 of InternationalPublication No. WO 2003/048214.

Formulation: TFE/PPVE=94.4/5.6 (mass %)

MFR: 14.5 (g/10 min)

Melting point: 302° C.

Number of functional groups: 271/10⁶ C

Test pieces were produced and an immersion test in an electrolyticsolution was carried out using the obtained test pieces in the samemanner as in Example 1, except that the above-described pellets wereused. The results are shown in the FIGURE. Test pieces were produced andthe compression set rate and the temperature for retaining 2 MPa weredetermined using the obtained test pieces in the same manner as inExample 1, except that the above-described pellets were used. Theresults are shown in Table 3.

TABLE 3 Comparative Example 1 Example 1 Example 2 Example 3 CS (50%,150° C.) [%] 99.56 99.46 99.52 98.97 CS (50%, 170° C.) [%] 99.97 99.9199.95 99.70 CS (50%, 190° C.) [%] 100.42 100.27 100.35 100.13 2 MParetention [° C.] 155 159 157 168 temperature

What is claimed is:
 1. A member for a non-aqueous electrolyte battery,comprising: a copolymer containing a tetrafluoroethylene unit and afluoroalkyl vinyl ether unit, wherein the number of functional groupsper 10⁶ carbon atoms of a main chain of the copolymer is 100 or less,and a melt flow rate of the copolymer is less than 20 g/10 minutes. 2.The member for a non-aqueous electrolyte battery according to claim 1,wherein the copolymer has a melting point of 295° C. to 320° C.
 3. Themember for a non-aqueous electrolyte battery according to claim 1,wherein a content of the fluoroalkyl vinyl ether unit in the copolymeris 1.0 to 10.0 mass % based on all monomer units.
 4. The member for anon-aqueous electrolyte battery according to claim 1, wherein thefluoroalkyl vinyl ether unit is a perfluoro(propyl vinyl ether) unit. 5.The member for a non-aqueous electrolyte battery according to claim 1,wherein the member is used in a compressively deformed state at acompressive deformation rate of 10% or more.
 6. The member for anon-aqueous electrolyte battery according to claim 1, comprising: aliquid-contact surface with a non-aqueous electrolytic solution.
 7. Themember for a non-aqueous electrolyte battery according to claim 1,wherein an amount of fluorine ions eluted and detected in an immersiontest in an electrolytic solution is 1 ppm or less.
 8. The member for anon-aqueous electrolyte battery according to claim 1, wherein the memberis an injection molded article.
 9. The member for a non-aqueouselectrolyte battery according to claim 1, wherein the member is asealing member or an insulating member.